Accidental Overexposure of Radiotherapy in Costa Rica - Article Example

Accidental Overexposure of Radiotherapy in Costa Rica Accidental Overexposure of Radiotherapy in Costa Rica The republic of CostaRica is a country located in Central America and has a total area of approximately 50,900 km2. A report in 1993, the republic had a population of about 3.22 million of which the male comprised of 1.63 million while the females were about 1.59 million. In a 1991 report, the capital city, San Jose had about 1.11 million inhabitants. The Costa Rican social security system, which is mandated to provide medical cover, reported 90% coverage for the population. The life expectancy was reported to be at 75.2 years between the years 1990 and 1995. Integral in the treatment of cancer in Costa Rica are three hospitals which also act as referral centres for the different segments of the country. These include the San Juan de Dios Hospital, the Rafael Angel Calderon Guardia Hospital and the Mexico Hospital. Of significance and relevant to the case study is the San Juan de Dios Hospital which has radiotherapy facilities (International Atomic Energy Agency, 1998). During the month of July 1997, the international atomic energy association received an invitation from the government of Costa Rica to aid in assessment of overexposure of radiotherapy. This overexposure had occurred to patients in San Jose Hospital in Costa Rica. The initiating occurrence specifically happened at San Juan de Dios hospital in San Jose on the 22nd of August, 1996. This was after a radioactive carbon source, 60 CO was replaced. When the new source was standardized, an inaccuracy was made in the computation of dose rate. Consequently, this error led to administration of considerable higher radiation doses compare to the prescribed intake in terms of exposure (International Atomic Energy Agency, 1998). The accident happened within the radiotherapy Alycon II unit of the radiotherapy facility within the hospital. The international atomic energy association in conjunction with the world health organization thermo luminescence dosimeters postal quality audits showed discrepancies since 1977. This was specific for the San Juan de Dios Hospital and the dose values as prescribed by these organizations were significantly altered. Because there was no satisfactory explanation as to these large disparities in dose values, an expert was engaged to evaluate the possibilities of such differences. The expert was to assess the physical aspects of quality assurance in radiotherapy. Furthermore, the expert was also to verify degree of application recommended by the technical report series and those of compliance reports. The review was conducted between the 8th and 19th of July, 1996. Her report indicated that there were no records kept on the calibration of beams emitted by radiation machines. Additionally, the assessment showed that there was no information available on the specific equipment used to offer radiotherapy services. With working environment prevailing in tandem with dose determination procedures properly followed, the outcome obtained or the calculation of absorbed dose rate in a computer program was not easily verifiable. The computer program which was developed by the person in charge of dosimeter had errors of close to 5% in percentage dose values. Moreover, there was an error of approximately 2 centimeters in the optical distance indicator (Perez & Brady, 1998). Discrepancies of up to 8% within the calculated time found, for the same irradiation conditions, when a calculation method on the basis of percentage depth dose (PDD) and the tissue air ratio (TAR) was used. Initial examination indicated that similar absorbed dose rate value had been employed in both procedures. Consequently, revelation on confusion between the concepts of dose in air and dose in water at the depth of optimal maximization was eminent. Having underpinned and satisfactorily addressed these issues, the expert brought these findings to radiation oncologists at the hospital. These included thermo luminescence dosimeters dose quality audits since 1989 as well as conceptual mistakes in computation. These revelations were received by a lot of skepticism from the radiation oncologists who said they would have noticed the errors in clinical outcomes. In her explanation, the expert stated that in all cases where doses were delivered via open radiation fields, thus no shielding of organs, doses were lower. It is imperative to note that lower doses can only be clinically detected after months or years in comparison to over dosage. The overall percentage of over dosage to patients undergoing radiotherapy at the moment was at 73% (International Atomic Energy Agency, 1998). On the basis of temporal categorization of the effects of radiation exposure at the high levels used in radiotherapy can be acute, sub acute and chronic. The impacts of the radiation overexposure in surviving patients of the accident were predominantly sub acute and chronic. A great number of patients who were overexposed to the radiation beams showed reactions such as vomiting and skin ulcerations. Additionally, these patients displayed signs of severe mucositis, diarrhea and nausea. However, the acute effects of the overexposure initially manifested were dependent on the body parts irradiated. In general, the effects monitored in patients resulted from overexposure of specific sensitive tissues or in a reduction in vascular supply of blood. With this regard, the most chronic impacts were consequences of irreversible narrowing of the lumina of small blood vessels particularly arterioles. In such occurrences, there are tremendous increases in the thickness of the arteriole walls. As a result, the size of the lumina within these vessels decreases thus reducing the supply of blood in the vascular tissues. The consequent eventuality is that these tissues may become thin or atrophic and in instances where reductions in blood supply is severe, such tissues undergo programmed cell death; necrosis. The changes in the vascular tissue may be progressive and may continue to be manifest in years after the exposure (Fletcher, 1980). The evaluation of patients who were exposed to such high dosages was not fully achieved because of a number of factors. A major task was to distinguish the adverse effects caused by radiation to those impacts of malignant disease conditions. Establishing radiation effects can in most cases be accomplished with knowledge of radiation sensitivity to tissues. Other factors include the known radiation dose, time course of expression of radiation effects and fractionation scheme. Lastly, the determination of radiation effects is dependent on the location of the radiation and the field size. In the situation under consideration, disparities in the radiation therapy protocols and practices were implemented in the treatment of the same medical conditions. Some of these procedures involve very large fields, with treatment of each field every other day. More than half the prescribed radiation therapy treatments had fewer than the normally accepted number of fractions. The critical physical problems caused by the overexposure of these patients relate to specific body systems. These care exemplified by the central nervous system, the skin, the gastrointestinal tract and the cardiovascular. These systems are extremely critical in this accident because of their sensitivity to radiation and also due to the fact that the tumors treated were majorly located in the neck, head and of pelvic origin Borrás, Barés, Rudder, Amer, Millán & Abuchaibe 2004). A number of patients experienced difficulties as a result of the irradiation in the brain, peripheral nerves and spinal cord. In general, the radiation of the brain leads to cortical atrophy in a large number of cases. Cortical atrophy due to overexposure led to changes in white matter, a condition called leukoencephalopathy and such patients suffered calcifications. Additionally, a number of the patients exhibited mineralizing microangiopathy. The children who had such overexposures following routine radiotherapy showed poor school performance and dysfunction of the pituitary gland as well as hypothalamus. Severe overexposure has detrimental effects including ataxia, spasticity, lethargy and progressive dementia. Changes within the brain resulting from radiation are equally potentiated by other chemotherapy and methotrexate. Cerebral necrosis is another serious and irrevocable complication of radiation induced disease of the vascular tissue. This condition induced by radiation occurs with moderate probability when therapy schemes exceed 40 Gy in 10 fractions. Brain necrosis may have symptoms such as intracranial pressure, headaches, psychotic changes and seizures. Radiation overexposure to the central nervous system may lead to optical nerve damage and blindness. This happens in patients who receive more than 42 Gy in 15 fractions. Loss of hearing is also well documented in cases where patients receive more than 65 Gy in standard factions. Higher or shorter fractionation schemes can also lead to necrosis of the ossicles (International Atomic Energy Agency, 1998). Irradiation of the spinal cord can also result in radiation myelitis, which can be short-lived or irreversible. Acute myelitis in most cases appears after 2 to 4 months after exposure and lesions appear to be caused by temporary demyelination of the motor neurons. Such patients exhibit Lhermitte’s sign, which occurs with neck flexion or other body movements that stretch the spinal cord. About 10% o the overexposed patients were and continue to be at a risk of spinal cord effects. The backbone is a relatively radiosensitive organ and overexposure can have detrimental effects. Peripheral nerves can also be impacted by overexposure to radiation beams although they show a bit of resistance. Doses within the range of 50 Gy in 25 fractions over a period of 5 weeks led to brachial plexus injury in patients. Such patients complained of pain in the sacral vertebrae and may have resulted to neuropathy (International Atomic Energy Agency, 1998). With elevated doses of radiation beam, acute exudative skin reaction is often followed by temporary regeneration. Therefore, healing of the initial reaction should not be taken as a sign that no considerable overexposure took place or that late effects can be ruled out. Changes in the skin include thin dry semi translucent pigmentation, fibrosis and telangiectasia. Areas mostly affected are those that experience friction and moist conditions such as axilla, skin folds and the groin. With chronic radiation changes, the skins break down due to mechanical an ultraviolet trauma. This vital body system becomes easily infected and experiences difficulties in healing as well as ulceration. A majority of the patients received skin doses of higher than 52 Gy with less than 20 fractions. This resulted in severe fibrosis, fixed skin and in others skin necrosis. The effects were exacerbated by treatment with anterior field one day followed by a posterior treatment the next day. This was in contrary to treatment with each field every day (Borrás, Barés, Rudder, Amer, Millán & Abuchaibe 2004). Within the gastrointestinal tract, specifically the intestine is very sensitive to radiation. In this particular accident, a number of patients were irradiated to rather large fields of the lower abdominal portion. These areas were irradiated at higher doses with minimal fractions. Harsh chronic radiation injury of the ileum and small bowel presents stenosis, abdominal pain and constipation. Moreover, there were cases of acute abdomen ulcerations, fistulas, perforation and infarction. Additionally, patients experienced radiation injury to the rectum and sigmoid with bouts of rectal bleeding after 6 to 12 months (Jung, Beck-Bornholdt, Svoboda, Alberti & Herrmann, 2001). Radiation induced changes within the cardiac system were reported in patients undergoing treatment of Hodgkin’s disease. Cardiomyopathy seldom occurs with standard fractionation schemes and doses less than 40 Gy. However, more than half of the patients who received more than 40 Gy dose level complained of pericarditis. Particularly, a patient who received 53 Gy in 17 fractions subsequently developed pericardial effusion when the exposure was done on the mediastinum. Radiation can also impact major blood vessels. It results in increase coronary heart disease and high incidence of arteriosclerosis of the aorta, brachial and pelvic vessels (International Atomic Energy Agency, 1998). References Borrás, C., Barés, J., Rudder, D., Amer, A., Millán, F., & Abuchaibe, O. (2004). Clinical effects in a cohort of cancer patients overexposed during external-beam pelvic radiation. International Journal of Radiation Oncology , 538-550. Fletcher, G. H. (1980). Textbook of radiotherapy. Philadelphia: Lea & Febiger. International Atomic Energy Agency. (1998). Accidental Overexposure of Radiotherapy Patients in San Jose, Costa Rica. Radiation Oncology , 1-173. Jung, H., Beck-Bornholdt, H., Svoboda, V., Alberti, W., & Herrmann, T. (2001). Quantification of late complications after radiation therapy. Radiotherapy Oncology , 233-246. Perez, C., & Brady, L. (1998). Principles and practice of radiation oncology. Philadelphia: Lippincott Williams & Wilkins. Read More